Preheat the oven to 450?. Slice the broccoli stalk crosswise and florets lengthwise ¼ inch thick. Transfer to a rimmed baking sheet and add sliced lemon, olive oil and red pepper, season with salt, and toss to coat. Roast for about 10 minutes, or until lightly browned. Stir in sesame seeds and roast until broccoli is tender, about 10 more minutes.

Meanwhile, in a small bowl, whisk the yogurt with tahini, lemon juice, garlic and season with salt. Spread the yogurt sauce on platter and top with broccoli. Serve warm.